Kill index analysis for automatic defect classification in semiconductor wafers

Abstract

A kill index classification method for prioritizing relational aspects of topological defect intersections, particularly in association with an intermediate analytical testing stage of a multi-stage semiconductor fabrication process. The method relates to an analysis of the geometrical relationship between non-predetermined portion(s), generally referred to as defects, and the surrounding predetermined topology of a conductive semiconductor pattern, to determine the effect of defects on the functionality and reliability of a wafer, and particularly an examined die thereon. Further, in accordance with this geometrical information, a preferred classification of the effects of defects into a numerical value, the "kill index", is achieved. Preferably, this kill index is strongly linked, correlated and related to the damage caused by the defect to the functionality and/or reliability of the underlying integrated circuit.

What is claimed is:  
     
       1. In a semiconductor fabrication process, a kill index classification method for prioritizing relational aspects of topological defect intersections, said method including the steps of 
       a) locating a region having at least one non-predetermined portion therein;  
       b) determining a predetermined topology for the region;  
       c) calculating evaluation parameters based on the at least one non-predetermined portion in relation to the predetermined topology for the region; and  
       d) assigning a kill index classification using the calculated evaluation parameters.  
     
     
       2. The kill index classification method according to  claim 1  wherein the step of locating a region having at least one non-predetermined portion therein includes the steps of 
       a1) accepting at least one appropriate resolution image of the region; and  
       a2) using the at least one appropriate resolution image, analyzing the region to determine if there is a rule violating shaped portion located therein.  
     
     
       3. The kill index classification method according to  claim 2   
       wherein the step of accepting at least one appropriate resolution image of the region includes the steps of  
       i) accepting a reference image, and  
       ii) accepting a defect image, and  
       wherein the step of analyzing the region to determine if there is a rule violating shaped portion located therein includes the step of comparing the reference image with the defect image.  
     
     
       4. The kill index classification method according to  claim 2   
       wherein the step of accepting at least one appropriate resolution image of the region includes the steps of  
       i) accepting a reference map, and  
       ii) accepting a defect image, and  
       wherein the step of analyzing the region to determine if there is a rule violating shaped portion located therein in includes the step of comparing the reference map with the defect image.  
     
     
       5. The kill index classification method according to  claim 2   
       wherein the step of accepting at least one appropriate resolution image of the region includes the steps of  
       i) accepting a reference rule set, and  
       ii) accepting a defect image; and  
       wherein the step of analyzing the region to determine if there is a rule violating shaped portion located therein includes the step of comparing the reference rule set with the defect image.  
     
     
       6. The kill index classification method according to  claim 5  wherein the reference rule set includes a threshold for at least one topological feature selected from the list of 
       i) a detected edge discontinuity,  
       ii) a detected edge curvature,  
       iii) an interior angle formed from two intersecting detected edges,  
       iv) an exterior angle formed from two intersecting detected edges, or  
       v) a fabrication mask topology design principle.  
     
     
       7. The kill index classification method according to  claim 1  wherein the step of determining a predetermined topology for the region includes at least one step selected from the list of 
       i) examining a reference image;  
       ii) examining a reference map; or  
       iii) examining a fabrication mask topology design algorithm methodology used to produce the reference map.  
     
     
       8. The kill index classification method according to  claim 1  wherein the step of calculating evaluation parameters based on the at least one non-predetermined portion in relation to the predetermined topology for the region includes the step of assigning a topology intersection parameter for the juxtaposition of the at least one non-predetermined portion with the predetermined topology. 
     
     
       9. The kill index classification method according to  claim 1  wherein the step of assigning a kill index classification using the calculated evaluation parameters includes convoluting the calculated evaluation parameters into a numeric classification. 
     
     
       10. The kill index classification method according to  claim 1  wherein the step of assigning a kill index classification using the calculated evaluation parameters includes convoluting the calculated evaluation parameters into a multi-parametric classification coordinate. 
     
     
       11. The kill index classification method according to  claim 1  wherein the step of locating a region having at least one non-predetermined portion therein includes locating a region having at least one defect footprint. 
     
     
       12. The kill index classification method according to  claim 11  wherein locating a region having at least one defect footprint includes locating a region having at least one multi-component footprint. 
     
     
       13. The kill index classification method according to  claim 1  wherein the step of calculating evaluation parameters based on the at least one non-predetermined portion in relation to the predetermined topology for the region includes said at least one non-predetermined portion having at least one non-predetermined portion core class selected from the list: 
       a) at least one pattern non-predetermined portion selected from the list:  
       i) extra pattern connected,  
       ii) extra pattern isolated,  
       iii) missing pattern, and  
       iv) deformed pattern; or  
       b) at least one non-predetermined particle portion selected from the list:  
       i) crater in pattern,  
       ii) crater in background,  
       iii) particle on pattern,  
       iv) particle on background,  
       v) particle on distortion,  
       vi) embedded under pattern, and  
       vii) embedded under background.  
     
     
       14. The kill index classification method according to  claim 1  wherein the step of calculating evaluation parameters based on the at least one non-predetermined portion in relation to the predetermined topology for the region includes said evaluation parameters having at least one parameter selected from the list: 
       a) a non-predetermined portion isolated from the predetermined topology;  
       b) a non-predetermined portion close to the predetermined topology;  
       c) a non-predetermined portion connected to the predetermined topology;  
       d) a non-predetermined portion bridging the predetermined topology; and  
       e) a non-predetermined portion close to bridging the predetermined topology.  
     
     
       15. The kill index classification method according to  claim 14  wherein said non-predetermined portion isolated from the predetermined topology includes a distance greater than a predetermined distance between the at least one non-predetermined portion and a pattern portion of the predetermined topology. 
     
     
       16. The kill index classification method according to  claim 14  wherein said non-predetermined portion close to the predetermined topology includes a distance less than a predetermined distance between the at least one non-predetermined portion and a pattern portion of the predetermined topology. 
     
     
       17. The kill index classification method according to  claim 14  wherein said non-predetermined portion connected to the predetermined topology includes the at least one non-predetermined portion being in contact with a pattern portion of the predetermined topology. 
     
     
       18. The kill index classification method according to  claim 14  wherein said non-predetermined portion bridging the predetermined topology includes at least one parameter selected from the list: 
       a) at least one non-predetermined portion connecting at least two pattern portions of the predetermined topology;  
       b) at least one non-predetermined portion connecting at least one pattern portion and intersecting at least one other pattern portion of the predetermined topology; and  
       c) at least one non-predetermined portion intersecting at least two pattern portions of the predetermined topology.  
     
     
       19. The kill index classification method according to  claim 14  wherein said non-predetermined portion close to bridging the predetermined topology includes the at least one non-predetermined portion being close to at least two pattern portions of the predetermined topology. 
     
     
       20. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform a kill index classification method for prioritizing relational aspects of topological defect intersections in a semiconductor fabrication process, said method including the steps of: 
       a) locating a region having at least one non-predetermined portion therein;  
       b) determining a predetermined topology for the region;  
       c) calculating evaluation parameters based on the at least one non-predetermined portion in relation to the predetermined topology for the region; and  
       d) assigning a kill index classification using the calculated evaluation parameters.  
     
     
       21. A method according to  claim 1 , wherein said semiconductor fabrication process is a multi-stage semiconductor fabrication process, and wherein said kill index classification method is performed after each stage of said multi-stage semiconductor fabrication process. 
     
     
       22. A method according to  claim 21 , wherein said semiconductor fabrication process is a multi-stage semiconductor fabrication process, and wherein said kill index classification method is performed after each stage of said multi-stage semiconductor fabrication process.